Property, Plant and Equipment (Narrative) (Detail) $ in Millions	1 Months Ended		3 Months Ended		9 Months Ended
	Nov. 30, 2021 USD ($)	Aug. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) MW	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Property Plant And Equipment [Line Items]
Property, plant and equipment			$ 58,386		$ 58,386		$ 57,848	[1]
Impairment of assets and other charges (benefits)			(222)	$ 1,151	194	$ 1,963
Dominion Energy
Property Plant And Equipment [Line Items]
Impairment of assets and other charges (benefits)				665		665
Asset impairment charges after tax				293		293
Impairment of assets and other charges attributable to noncontrolling interest				267		267
Property, plant and equipment down to estimated fair value						1,400
Terra Nova Renewable Partners | Nonregulated Solar Projects | SBL Holdco
Property Plant And Equipment [Line Items]
Percentage of controlling interest		67.00%
Consideration		$ 456
Gain (loss) on held for sale					30
Gain (loss) on held for sale, after tax					31
Property, plant and equipment			743		743
Long-term debt			339		339
Clearway | Four Brothers and Three Cedars
Property Plant And Equipment [Line Items]
Percentage of controlling interest		50.00%
Consideration		$ 335
Gain (loss) on held for sale					225
Gain (loss) on held for sale, after tax					170
Property, plant and equipment			744		744
Long-term debt			75		75
Virginia Electric and Power Company
Property Plant And Equipment [Line Items]
Property, plant and equipment			33,876		33,876		$ 32,569	[2]
Impairment of assets and other charges (benefits)			(230)	$ 200	(269)	$ 1,008
Virginia Electric and Power Company | Virginia Regulation
Property Plant And Equipment [Line Items]
Impairment of assets and other charges (benefits)			318
Wexpro | Scenario Forecast
Property Plant And Equipment [Line Items]
Asset acquisition, total consideration	$ 41
Acquisition of Solar Project at Schools in Virginia
Property Plant And Equipment [Line Items]
Anticipated projected cost			$ 65		$ 65
Aggregate generation capacity | MW					32

[1] Dominion Energy’s Consolidated Balance Sheet at December 31, 2020 has been derived from the audited Consolidated Balance Sheet at that date.

[2] Virginia Power’s Consolidated Balance Sheet at December 31, 2020 has been derived from the audited Consolidated Balance Sheet at that date.